1. Field of the Invention
The present invention relates to a semiconductor element driving circuit for controlling switching of a semiconductor element, and a semiconductor device with the semiconductor element and the semiconductor element driving circuit.
2. Description of the Background Art
A semiconductor element driving circuit disclosed for example as a driving control circuit of Japanese Patent Application Laid-Open No. 2010-226835, or as a semiconductor element control device of Japanese Patent Application Laid-Open No. 2009-44304, is capable of providing stable operation of a power semiconductor switching element as a semiconductor element even if a power supply voltage supplied to the semiconductor element fluctuates.
The reference voltage of the conventional semiconductor element driving circuit is generally set at a fixed value. The reference voltage is normally applied to the source electrode of a transistor.
It is assumed for example that the reference voltage is determined based on the ground, and that a semiconductor element to be driven requires a high gate-to-source voltage Vgs during the semiconductor element is ON. In this case, the fluctuation of a power supply voltage VCC makes the gate-to-source voltage Vgs applied to the semiconductor element fluctuate while the semiconductor element makes an ON operation, resulting in a problem of nonuniform current capability of the semiconductor element.
It is also assumed for example that the reference voltage is determined based on the power supply voltage VCC, and that a semiconductor element to be driven requires a relatively low threshold voltage Vth. In this case, the fluctuation of the power supply voltage VCC makes the gate-to-source voltage Vgs applied to the semiconductor element fluctuate while the semiconductor element makes an OFF operation, resulting in a problem of nonuniform turn-off loss of the semiconductor element.